DESCRIPTIONxmlTreeGetExternalSubset() gets the external DTD subset from the
XML document doc. This is the part of the DTD that is defined
via a SYSTEM reference, as opposed to the internal subset, which is
defined within the XML file itself.

Note that the XML file must be parsed with the option
XML_PARSE_DTDLOAD, otherwise the external DTD will not be
loaded.

EXAMPLE

<$dtd = (xmlTreeGetExternalSubset($doc))>

CAVEATSParsing the external DTD may involve performing a network fetch. This
can be disabled by adding XML_PARSE_NONET to the parsing
options.